One of the most active and challenging fields in molecular biology today is the genetic study of eukaryotic systems. An essential, but often rate limiting step in this area is the screening of DNA libraries for gene isolation. This procedure uses radiolabel hybridization techniques and autoradiography to achieve the required sensitivity and specificity. The particular part of the process which this proposal addresses is the measurement of the distribution of radioactivity on the hybridization membrane which normally measured with a 16 to 24 hour autoradiograph. We propose to develop a new, large area, real-time imaging system for this application. Ultimately, this instrument should be able to provide images over a 1m2 are with 0.5 mm spatial resolution in less than one hour. Using this new approach, not only will the researcher be able to harvest pure genetic material without the need to suffer the delays of autoradiography, but will also be able to carry out the procedure with much higher level of confidence. Furthermore, if this new instrument is made compatible with modern laboratory instruments, the entire process of identifying and selecting DNA clones could be automated.